1. Field of the Invention
The invention relates to a high-pass filtering process for focusing images, particularly digital or similar images, which are composed of a plurality of single dot areas, named pixels having different individually variable luminous intensities, so as to generate all together an image. More particularly, the filtering process provides for each pixel of the image a correction of the intensity value of said pixel, which is calculated statistically, on the basis of combinations of high-pass filterings performed in at least one, and preferably in at least four, different directions with respect to the matrix of the pixels forming the image.
2. Description of Related Art
In prior art methods, each pixel under examination is subjected to high-pass filtering in multiple directions, using high-pass monodirectional filters. Then, the results of each monodirectional high-pass filtering are combined, after being weighted, to obtain statistical corrections of the filtered pixel.
These prior art high-pass filtering methods ensure, on the one hand, that the image is well focused, that is provided with sharp outlines, but may cause, at the same time, the outlines having intensity variations to a certain substantial extent, to shift, and thus involve a certain level of deformation in the reproduced image as compared to the real shape of the corresponding object. This is a very serious drawback, particularly in image in acquisition devices, such as those for image acquisition by echography or by nuclear magnetic resonance. In this case, a high level of correspondence between the real shape and the reproduced image, as well as a high level of sharpness and clarity are extremely important.